Understanding Bioaccumulation & Impact of Environmental Endocrine Disruptors on Health, Slides of Public Health

Download Understanding Bioaccumulation & Impact of Environmental Endocrine Disruptors on Health and more Slides Public Health in PDF only on Docsity! Environmental Endocrine Disruptors Part II: Bioaccumulation Ovaries (women)Testicles (men) Pancreas Adrenal glands Hypothalamus Thyroid gland Parathyroidgland Pineal gland Pituitary gland docsity.com Course Objectives  Understand the terms used, particularly those having direct relevancy to chemical bioaccumulation. Appreciate the factors and the activities affecting chemical bioaccumulation.  Be familiar with the criteria used for qualifying a pollutant as a bioaccumulant.  Undertake a brief review of the methods and models available for the quantification of bioaccumulation potential. docsity.com Uptake of Bioaccumulants  The uptake of many bioaccumulants by organisms is typically initiated by passive transport, as chemical molecules tend to move from high to low concentration.  This first step is affected by the bioaccu- mulant’s lipophilicity and water solubility.  Some chemicals also have a high affinity for binding with proteins or the ability to dissolve in fats, thus prolonging the storage of these substances inside an organism. docsity.com Bioactivity of Pollutants  Accumulation of an endocrine disruptor inside an organism will pose threat of interference only if the contaminant is in a form active for binding to hormonal sites.  Bioaccumulants having the affinity to bind to plasma proteins are less biologically available or active for hormonal disruption. Many environmental endocrine disruptors are more bioactive, compared to endogenous steroid hormones. docsity.com Mobility of Pollutants  Persistent endocrine disruptors can reach remote regions via atmospheric, oceanic, or terrestrial transport. Animal migration (biotransport) is the fourth mode of long-range transport of bioaccumulants.  Biotransport appears to be much more significant than the other three modes, in part because the contaminant loads are more localized and in part because the contaminants are more biologically active. docsity.com Metabolites of Pollutants Metabolites of some persistent organic pollutants are more bioactive as endocrine disruptors.  Some metabolites, such as DDE, have their own unique active roles as an endocrine disruptor that their parents do not have.  PCBs are other examples known to have metabolites with hormonal activities more potent and, in some instances, different than those of their parents. docsity.com Other Factors Affecting Bioactivity  Not all metabolites of endocrine disruptors are more biologically active or available; some metabolites are less active than their parent compounds.  Some endocrine disruptors can disable the osmoregulatory system of a bioaccumulating organism (e.g., a young salmon), by inter- fering with the estrogenic effects in this organism; it is this osmoregulatory system that makes endocrine disruptors more bioactive. docsity.com BAF, BCF, BMF  Bioaccumulation Factor (BAF) is the ratio of a test chemical’s concentration in a test organism’s tissues to that in the surrounding medium, when all potential uptake mechanisms are included.  Bioconcentration Factor (BCF) is a specific case of BAF, when the uptake is only from the surrounding medium.  Biomagnification Factor (BMF) is the ratio of a test chemical’s concentration in the tissues of an organism, to that in the organism’s prey. docsity.com Bioconcentration Factor (I) Many bioconcentration factor (BCF) assessments are based on aquatic measure- ments because fish provides a rich lipophilic microenvironment for bioaccumulation.  BCF is typically measured as the ratio of the concentration of a chemical in a test organism to the chemical’s concentration in the surrounding medium.  For many lipophilic chemicals, BCFs can be calculated using the regression equation: log BCF = - 2.3 + 0.76 x (log Kow). docsity.com Bioconcentration Factor (II)  The bioconcentration factor (BCF) can be calculated from Kow, through use of the log- log QSAR relationship.  U.S. EPA has been using the BCFWIN software developed by SRC for measuring the BCFs for many chemicals.  SRC’s BCFWIN program is designed to estimate the BCF using the test chemical’s Kow, based on the log-log fit generalized from some 694 chemicals. docsity.com Bioconcentration Factor (III)  For a bioconcentration factor (BCF) to be estimated from a site-specific study, three (3) conditions should be met.  For a BCF to be estimated from a laboratory study, five (5) conditions should be met.  These conditions include: sufficient duration for observation; a subthreshold test levels; and the use of test guidelines acceptable to the regulatory authorities. docsity.com